This invention relates to a technique of utilizing information from many sensor nodes that are connected to a network, and more particularly, to a sensor network system capable of smoothly delivering information sent from the sensor nodes.
Sensor network system technology has been advancing in recent years. A sensor network system (hereinafter referred to as sensor net system) collects, via a network, sensing data which is obtained from many sensor nodes, and makes the information obtained from the many sensor nodes available over a network to computers and apparatuses that are located away from the sensor nodes.
In a sensor net system, information obtained by many sensor nodes is sent to a server computer or the like via relay stations or base stations, and the server computer gathers the information of the sensor nodes. The thus structured sensor net system has a possibility that too much amount of information from one sensor node causes a processing overload in a relay station or a base station that transfers the information, and accordingly a failure in collecting information from other nodes is generated. A technique for avoiding such a failure has been known in which a terminal whose communication characteristics (e.g., transmission intervals) deviate from average communication characteristics by a given degree or more is deemed as out of order and a server computer withholds sending of data to this terminal (see JP 2005-159646 A, for example).
Another avoidance technique has also been known in which a sensor node that sends a large amount of information is deemed as an abnormal sensor node and only information from normal sensor nodes is transmitted while information from any abnormal sensor nodes is discarded (see JP 11-120104 A, for example).